One of the causes of the noises generated by a pneumatic tire is a cavernous resonance resulting from vibration of the air with which the tire is filled. When a tire is rolled, uneven road surfaces cause a tread portion to vibrate. The vibrations of the tread portion cause the air inside the tire to vibrate, which produces this cavernous resonance.
As a method for reducing noise caused by such cavernous resonance, providing a sound absorbing member within a cavity portion formed between the tire and the rim of the wheel has been proposed. More specifically, a noise reduction device is formed of a band member and a sound absorbing member, the band member being made of a thermoplastic resin formed into a ring shape along a tire inner surface and the sound absorbing member being made of a porous material and bonded to the band member. The sound absorbing member is installed in a region corresponding to the tread portion on a tire inner surface with the help of an elastic restoring force of the band member (refer to Japanese Patent No. 4175479 and International Patent Application Publication No. WO/2005/012007, for example).
Nevertheless, in the noise reduction device described above, a rigidity of the band member becomes inadequate when a thickness of the band member is reduced to save weight, resulting in the problem that the sound absorbing member cannot be firmly secured to the tire inner surface. Then, when the sound absorbing member is not secured to the tire inner surface in a stable manner, problems may arise such as deterioration in rim assemblability, or failure of the noise reduction device to follow the travel of the tire, resulting in an increased susceptibility to fracturing.